Drive mechanism for a feed roller in a printer

Abstract

A drive mechanism for a feed roller in a printer, which includes a worm wheel connected to the feed roller and forming a rotary unit therewith, a worm engaging said worm wheel, a motor driving said worm, an encoder detecting increments (δφ) in an angular position of the worm, and a servo controller for the motor, wherein the rotary unit has a sync mark defining a reference position (φ 0 ), a reference detector is provided for detecting the sync mark, and said servo controller has access to a calibration memory and is adapted to output a calibrated motor control signal (C) dependant on the angular position of the feed roller as determined from said reference position (φ 0 ) and said worm angular position increments (δφ).

1 . A drive mechanism for a feed roller in a printer, which comprises: 
 a worm wheel provided on the feed roller and forming a rotary unit therewith,    a worm gear adapted to engage said worm wheel,    a motor for driving said worm,    an encoder for detecting incremental (δφ)angular positions of the worm, and    a servo controller operatively connected to the motor, wherein said rotary unit has a sync mark defining a reference position (φ 0 ), a reference detector is provided for detecting the sync mark, and the servo controller has access to a calibration memory and is adapted to output a calibrated motor control signal (C) dependant on the angular position of the feed roller as determined from said reference position (φ 0 ) and said worm angular position increments (δφ).    
   
   
       2 . The drive mechanism according to  claim 1 , wherein the sync mark is provided on the worm wheel.  
   
   
       3 . The drive mechanism according to  claim 2 , wherein the sync mark is formed by a gap in an annular boss formed on an end face of the worm wheel, and the reference detector is an optical detector embracing the boss.  
   
   
       4 . The drive mechanism according to  claim 1 , wherein the encoder is a quadrature encoder.  
   
   
       5 . The drive mechanism according to  claim 1 , including a control system which comprises said servo controller, a counter for counting pulses of the encoder, and a reference position register adapted to store a count value of said counter upon receipt of a detection signal from said reference detector.  
   
   
       6 . An ink jet printer containing the drive mechanism of  claim 1.